Ejemplo n.º 1
0
  def _setup_graph(self, n_inp, n_out, drop_frac, start_iter=1, end_iter=4,
                   freq_iter=2):
    """Setups a trivial training procedure for sparse training."""
    tf.reset_default_graph()
    optim = tf.train.GradientDescentOptimizer(0.1)
    sparse_optim = sparse_optimizers.SparseSETOptimizer(
        optim, start_iter, end_iter, freq_iter, drop_fraction=drop_frac)
    x = tf.random.uniform((1, n_inp))
    y = layers.masked_fully_connected(x, n_out, activation_fn=None)
    global_step = tf.train.get_or_create_global_step()
    weight = pruning.get_weights()[0]
    # There is one masked layer to be trained.
    mask = pruning.get_masks()[0]
    # Around half of the values of the mask is set to zero with `mask_update`.
    mask_update = tf.assign(
        mask,
        tf.constant(
            np.random.choice([0, 1], size=(n_inp, n_out), p=[1./2, 1./2]),
            dtype=tf.float32))
    loss = tf.reduce_mean(y)
    global_step = tf.train.get_or_create_global_step()
    train_op = sparse_optim.minimize(loss, global_step)

    # Init
    sess = tf.Session()
    init = tf.global_variables_initializer()
    sess.run(init)
    sess.run([mask_update])

    return sess, train_op, mask, weight, global_step
Ejemplo n.º 2
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 def testValueErrorOfGetGrowTensor(self, method):
     """Checks whether the new tensor is created with correct shape and type."""
     optim = tf.train.GradientDescentOptimizer(0.1)
     sparse_optim = sparse_optimizers.SparseSETOptimizer(
         optim, 0, 0, 1, use_stateless=False)
     weights = tf.random_uniform((3, 4))
     with self.assertRaises(ValueError):
         sparse_optim.get_grow_tensor(weights, method)
Ejemplo n.º 3
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 def testDtypeOfGetGrowTensor(self, dtype, init_type):
     """Checks whether the new tensor is created with correct data type."""
     optim = tf.train.GradientDescentOptimizer(0.1)
     sparse_optim = sparse_optimizers.SparseSETOptimizer(
         optim, 0, 0, 1, use_stateless=False)
     weights = tf.random_uniform((3, 4), dtype=dtype, maxval=5)
     grow_tensor = sparse_optim.get_grow_tensor(weights, init_type)
     self.assertEqual(grow_tensor.dtype, weights.dtype)
Ejemplo n.º 4
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 def testShapeOfGetGrowTensor(self, shape, init_type):
     """Checks whether the new tensor is created with correct shape."""
     optim = tf.train.GradientDescentOptimizer(0.1)
     sparse_optim = sparse_optimizers.SparseSETOptimizer(
         optim, 0, 0, 1, use_stateless=False)
     weights = tf.random_uniform(shape)
     grow_tensor = sparse_optim.get_grow_tensor(weights, init_type)
     self.assertAllEqual(weights.shape, grow_tensor.shape)
Ejemplo n.º 5
0
def main(unused_args):
    tf.set_random_seed(FLAGS.seed)
    tf.get_variable_scope().set_use_resource(True)
    np.random.seed(FLAGS.seed)

    # Load the MNIST data and set up an iterator.
    mnist_data = input_data.read_data_sets(FLAGS.mnist,
                                           one_hot=False,
                                           validation_size=0)
    train_images = mnist_data.train.images
    test_images = mnist_data.test.images
    if FLAGS.input_mask_path:
        reader = tf.train.load_checkpoint(FLAGS.input_mask_path)
        input_mask = reader.get_tensor('layer1/mask')
        indices = np.sum(input_mask, axis=1) != 0
        train_images = train_images[:, indices]
        test_images = test_images[:, indices]
    dataset = tf.data.Dataset.from_tensor_slices(
        (train_images, mnist_data.train.labels.astype(np.int32)))
    num_batches = mnist_data.train.images.shape[0] // FLAGS.batch_size
    dataset = dataset.shuffle(buffer_size=mnist_data.train.images.shape[0])
    batched_dataset = dataset.repeat(FLAGS.num_epochs).batch(FLAGS.batch_size)
    iterator = batched_dataset.make_one_shot_iterator()

    test_dataset = tf.data.Dataset.from_tensor_slices(
        (test_images, mnist_data.test.labels.astype(np.int32)))
    num_test_images = mnist_data.test.images.shape[0]
    test_dataset = test_dataset.repeat(FLAGS.num_epochs).batch(num_test_images)
    test_iterator = test_dataset.make_one_shot_iterator()

    # Set up loss function.
    use_model_pruning = FLAGS.training_method != 'baseline'

    if FLAGS.network_type == 'fc':
        cross_entropy_train, _ = mnist_network_fc(
            iterator.get_next(), model_pruning=use_model_pruning)
        cross_entropy_test, accuracy_test = mnist_network_fc(
            test_iterator.get_next(),
            reuse=True,
            model_pruning=use_model_pruning)
    else:
        raise RuntimeError(FLAGS.network + ' is an unknown network type.')

    # Remove extra added ones. Current implementation adds the variables twice
    # to the collection. Improve this hacky thing.
    # TODO test the following with the convnet or any other network.
    if use_model_pruning:
        for k in ('masks', 'masked_weights', 'thresholds', 'kernel'):
            # del tf.get_collection_ref(k)[2]
            # del tf.get_collection_ref(k)[2]
            collection = tf.get_collection_ref(k)
            del collection[len(collection) // 2:]
            print(tf.get_collection_ref(k))

    # Set up optimizer and update ops.
    global_step = tf.train.get_or_create_global_step()
    batch_per_epoch = mnist_data.train.images.shape[0] // FLAGS.batch_size

    if FLAGS.optimizer != 'adam':
        if not use_model_pruning:
            boundaries = [
                int(round(s * batch_per_epoch)) for s in [60, 70, 80]
            ]
        else:
            boundaries = [
                int(round(s * batch_per_epoch))
                for s in [FLAGS.lr_drop_epoch, FLAGS.lr_drop_epoch + 20]
            ]
        learning_rate = tf.train.piecewise_constant(
            global_step,
            boundaries,
            values=[
                FLAGS.learning_rate / (3.**i)
                for i in range(len(boundaries) + 1)
            ])
    else:
        learning_rate = FLAGS.learning_rate

    if FLAGS.optimizer == 'adam':
        opt = tf.train.AdamOptimizer(FLAGS.learning_rate)
    elif FLAGS.optimizer == 'momentum':
        opt = tf.train.MomentumOptimizer(learning_rate,
                                         FLAGS.momentum,
                                         use_nesterov=FLAGS.use_nesterov)
    elif FLAGS.optimizer == 'sgd':
        opt = tf.train.GradientDescentOptimizer(learning_rate)
    else:
        raise RuntimeError(FLAGS.optimizer + ' is unknown optimizer type')
    custom_sparsities = {
        'layer2': FLAGS.end_sparsity * FLAGS.sparsity_scale,
        'layer3': FLAGS.end_sparsity * 0
    }

    if FLAGS.training_method == 'set':
        # We override the train op to also update the mask.
        opt = sparse_optimizers.SparseSETOptimizer(
            opt,
            begin_step=FLAGS.maskupdate_begin_step,
            end_step=FLAGS.maskupdate_end_step,
            grow_init=FLAGS.grow_init,
            frequency=FLAGS.maskupdate_frequency,
            drop_fraction=FLAGS.drop_fraction,
            drop_fraction_anneal=FLAGS.drop_fraction_anneal)
    elif FLAGS.training_method == 'static':
        # We override the train op to also update the mask.
        opt = sparse_optimizers.SparseStaticOptimizer(
            opt,
            begin_step=FLAGS.maskupdate_begin_step,
            end_step=FLAGS.maskupdate_end_step,
            grow_init=FLAGS.grow_init,
            frequency=FLAGS.maskupdate_frequency,
            drop_fraction=FLAGS.drop_fraction,
            drop_fraction_anneal=FLAGS.drop_fraction_anneal)
    elif FLAGS.training_method == 'momentum':
        # We override the train op to also update the mask.
        opt = sparse_optimizers.SparseMomentumOptimizer(
            opt,
            begin_step=FLAGS.maskupdate_begin_step,
            end_step=FLAGS.maskupdate_end_step,
            momentum=FLAGS.s_momentum,
            frequency=FLAGS.maskupdate_frequency,
            drop_fraction=FLAGS.drop_fraction,
            grow_init=FLAGS.grow_init,
            drop_fraction_anneal=FLAGS.drop_fraction_anneal,
            use_tpu=False)
    elif FLAGS.training_method == 'rigl':
        # We override the train op to also update the mask.
        opt = sparse_optimizers.SparseRigLOptimizer(
            opt,
            begin_step=FLAGS.maskupdate_begin_step,
            end_step=FLAGS.maskupdate_end_step,
            grow_init=FLAGS.grow_init,
            frequency=FLAGS.maskupdate_frequency,
            drop_fraction=FLAGS.drop_fraction,
            drop_fraction_anneal=FLAGS.drop_fraction_anneal,
            initial_acc_scale=FLAGS.rigl_acc_scale,
            use_tpu=False)
    elif FLAGS.training_method == 'snip':
        opt = sparse_optimizers.SparseSnipOptimizer(
            opt,
            mask_init_method=FLAGS.mask_init_method,
            default_sparsity=FLAGS.end_sparsity,
            custom_sparsity_map=custom_sparsities,
            use_tpu=False)
    elif FLAGS.training_method in ('scratch', 'baseline', 'prune'):
        pass
    else:
        raise ValueError('Unsupported pruning method: %s' %
                         FLAGS.training_method)

    train_op = opt.minimize(cross_entropy_train, global_step=global_step)

    if FLAGS.training_method == 'prune':
        hparams_string = (
            'begin_pruning_step={0},sparsity_function_begin_step={0},'
            'end_pruning_step={1},sparsity_function_end_step={1},'
            'target_sparsity={2},pruning_frequency={3},'
            'threshold_decay={4}'.format(FLAGS.prune_begin_step,
                                         FLAGS.prune_end_step,
                                         FLAGS.end_sparsity,
                                         FLAGS.pruning_frequency,
                                         FLAGS.threshold_decay))
        pruning_hparams = pruning.get_pruning_hparams().parse(hparams_string)
        pruning_hparams.set_hparam(
            'weight_sparsity_map',
            ['{0}:{1}'.format(k, v) for k, v in custom_sparsities.items()])
        print(pruning_hparams)
        pruning_obj = pruning.Pruning(pruning_hparams, global_step=global_step)
        with tf.control_dependencies([train_op]):
            train_op = pruning_obj.conditional_mask_update_op()
    weight_sparsity_levels = pruning.get_weight_sparsity()
    global_sparsity = sparse_utils.calculate_sparsity(pruning.get_masks())
    tf.summary.scalar('test_accuracy', accuracy_test)
    tf.summary.scalar('global_sparsity', global_sparsity)
    for k, v in zip(pruning.get_masks(), weight_sparsity_levels):
        tf.summary.scalar('sparsity/%s' % k.name, v)
    if FLAGS.training_method in ('prune', 'snip', 'baseline'):
        mask_init_op = tf.no_op()
        tf.logging.info('No mask is set, starting dense.')
    else:
        all_masks = pruning.get_masks()
        mask_init_op = sparse_utils.get_mask_init_fn(all_masks,
                                                     FLAGS.mask_init_method,
                                                     FLAGS.end_sparsity,
                                                     custom_sparsities)

    if FLAGS.save_model:
        saver = tf.train.Saver()
    init_op = tf.global_variables_initializer()
    hyper_params_string = '_'.join([
        FLAGS.network_type,
        str(FLAGS.batch_size),
        str(FLAGS.learning_rate),
        str(FLAGS.momentum), FLAGS.optimizer,
        str(FLAGS.l2_scale), FLAGS.training_method,
        str(FLAGS.prune_begin_step),
        str(FLAGS.prune_end_step),
        str(FLAGS.end_sparsity),
        str(FLAGS.pruning_frequency),
        str(FLAGS.seed)
    ])
    tf.io.gfile.makedirs(FLAGS.save_path)
    filename = os.path.join(FLAGS.save_path, hyper_params_string + '.txt')
    merged_summary_op = tf.summary.merge_all()

    # Run session.
    if not use_model_pruning:
        with tf.Session() as sess:
            summary_writer = tf.summary.FileWriter(
                FLAGS.save_path, graph=tf.get_default_graph())
            print('Epoch', 'Epoch time', 'Test loss', 'Test accuracy')
            sess.run([init_op])
            tic = time.time()
            with tf.io.gfile.GFile(filename, 'w') as outputfile:
                for i in range(FLAGS.num_epochs * num_batches):
                    sess.run([train_op])

                    if (i % num_batches) == (-1 % num_batches):
                        epoch_time = time.time() - tic
                        loss, accuracy, summary = sess.run([
                            cross_entropy_test, accuracy_test,
                            merged_summary_op
                        ])
                        # Write logs at every test iteration.
                        summary_writer.add_summary(summary, i)
                        log_str = '%d, %.4f, %.4f, %.4f' % (
                            i // num_batches, epoch_time, loss, accuracy)
                        print(log_str)
                        print(log_str, file=outputfile)
                        tic = time.time()
            if FLAGS.save_model:
                saver.save(sess, os.path.join(FLAGS.save_path, 'model.ckpt'))
    else:
        with tf.Session() as sess:
            summary_writer = tf.summary.FileWriter(
                FLAGS.save_path, graph=tf.get_default_graph())
            log_str = ','.join([
                'Epoch', 'Iteration', 'Test loss', 'Test accuracy',
                'G_Sparsity', 'Sparsity Layer 0', 'Sparsity Layer 1'
            ])
            sess.run(init_op)
            sess.run(mask_init_op)
            tic = time.time()
            mask_records = {}
            with tf.io.gfile.GFile(filename, 'w') as outputfile:
                print(log_str)
                print(log_str, file=outputfile)
                for i in range(FLAGS.num_epochs * num_batches):
                    if (FLAGS.mask_record_frequency > 0
                            and i % FLAGS.mask_record_frequency == 0):
                        mask_vals = sess.run(pruning.get_masks())
                        # Cast into bool to save space.
                        mask_records[i] = [
                            a.astype(np.bool) for a in mask_vals
                        ]
                    sess.run([train_op])
                    weight_sparsity, global_sparsity_val = sess.run(
                        [weight_sparsity_levels, global_sparsity])
                    if (i % num_batches) == (-1 % num_batches):
                        epoch_time = time.time() - tic
                        loss, accuracy, summary = sess.run([
                            cross_entropy_test, accuracy_test,
                            merged_summary_op
                        ])
                        # Write logs at every test iteration.
                        summary_writer.add_summary(summary, i)
                        log_str = '%d, %d, %.4f, %.4f, %.4f, %.4f, %.4f' % (
                            i // num_batches, i, loss, accuracy,
                            global_sparsity_val, weight_sparsity[0],
                            weight_sparsity[1])
                        print(log_str)
                        print(log_str, file=outputfile)
                        mask_vals = sess.run(pruning.get_masks())
                        if FLAGS.network_type == 'fc':
                            sparsities, sizes = get_compressed_fc(mask_vals)
                            print('[COMPRESSED SPARSITIES/SHAPE]: %s %s' %
                                  (sparsities, sizes))
                            print('[COMPRESSED SPARSITIES/SHAPE]: %s %s' %
                                  (sparsities, sizes),
                                  file=outputfile)
                        tic = time.time()
            if FLAGS.save_model:
                saver.save(sess, os.path.join(FLAGS.save_path, 'model.ckpt'))
            if mask_records:
                np.save(os.path.join(FLAGS.save_path, 'mask_records'),
                        mask_records)
Ejemplo n.º 6
0
def train_function(training_method, loss, cross_loss, reg_loss, output_dir,
                   use_tpu):
    """Training script for resnet model.

  Args:
   training_method: string indicating pruning method used to compress model.
   loss: tensor float32 of the cross entropy + regularization losses.
   cross_loss: tensor, only cross entropy loss, passed for logging.
   reg_loss: tensor, only regularization loss, passed for logging.
   output_dir: string tensor indicating the directory to save summaries.
   use_tpu: boolean indicating whether to run script on a tpu.

  Returns:
    host_call: summary tensors to be computed at each training step.
    train_op: the optimization term.
  """

    global_step = tf.train.get_global_step()

    steps_per_epoch = FLAGS.num_train_images / FLAGS.train_batch_size
    current_epoch = (tf.cast(global_step, tf.float32) / steps_per_epoch)
    learning_rate = lr_schedule(current_epoch)
    if FLAGS.use_adam:
        # We don't use step decrease for the learning rate.
        learning_rate = FLAGS.base_learning_rate * (FLAGS.train_batch_size /
                                                    256.0)
        optimizer = tf.train.AdamOptimizer(learning_rate=learning_rate)
    else:
        optimizer = tf.train.MomentumOptimizer(learning_rate=learning_rate,
                                               momentum=FLAGS.momentum,
                                               use_nesterov=True)

    if use_tpu:
        # use CrossShardOptimizer when using TPU.
        optimizer = contrib_tpu.CrossShardOptimizer(optimizer)

    if training_method == 'set':
        # We override the train op to also update the mask.
        optimizer = sparse_optimizers.SparseSETOptimizer(
            optimizer,
            begin_step=FLAGS.maskupdate_begin_step,
            end_step=FLAGS.maskupdate_end_step,
            grow_init=FLAGS.grow_init,
            frequency=FLAGS.maskupdate_frequency,
            drop_fraction=FLAGS.drop_fraction,
            drop_fraction_anneal=FLAGS.drop_fraction_anneal,
            stateless_seed_offset=FLAGS.seed)
    elif training_method == 'static':
        # We override the train op to also update the mask.
        optimizer = sparse_optimizers.SparseStaticOptimizer(
            optimizer,
            begin_step=FLAGS.maskupdate_begin_step,
            end_step=FLAGS.maskupdate_end_step,
            grow_init=FLAGS.grow_init,
            frequency=FLAGS.maskupdate_frequency,
            drop_fraction=FLAGS.drop_fraction,
            drop_fraction_anneal=FLAGS.drop_fraction_anneal,
            stateless_seed_offset=FLAGS.seed)
    elif training_method == 'momentum':
        # We override the train op to also update the mask.
        optimizer = sparse_optimizers.SparseMomentumOptimizer(
            optimizer,
            begin_step=FLAGS.maskupdate_begin_step,
            end_step=FLAGS.maskupdate_end_step,
            momentum=FLAGS.s_momentum,
            frequency=FLAGS.maskupdate_frequency,
            drop_fraction=FLAGS.drop_fraction,
            grow_init=FLAGS.grow_init,
            stateless_seed_offset=FLAGS.seed,
            drop_fraction_anneal=FLAGS.drop_fraction_anneal,
            use_tpu=use_tpu)
    elif training_method == 'rigl':
        # We override the train op to also update the mask.
        optimizer = sparse_optimizers.SparseRigLOptimizer(
            optimizer,
            begin_step=FLAGS.maskupdate_begin_step,
            end_step=FLAGS.maskupdate_end_step,
            grow_init=FLAGS.grow_init,
            frequency=FLAGS.maskupdate_frequency,
            drop_fraction=FLAGS.drop_fraction,
            stateless_seed_offset=FLAGS.seed,
            drop_fraction_anneal=FLAGS.drop_fraction_anneal,
            initial_acc_scale=FLAGS.rigl_acc_scale,
            use_tpu=use_tpu)
    elif training_method == 'snip':
        optimizer = sparse_optimizers.SparseSnipOptimizer(
            optimizer,
            mask_init_method=FLAGS.mask_init_method,
            custom_sparsity_map=CUSTOM_SPARSITY_MAP,
            default_sparsity=FLAGS.end_sparsity,
            use_tpu=use_tpu)
    elif training_method in ('scratch', 'baseline'):
        pass
    else:
        raise ValueError('Unsupported pruning method: %s' %
                         FLAGS.training_method)
    # UPDATE_OPS needs to be added as a dependency due to batch norm
    update_ops = tf.get_collection(tf.GraphKeys.UPDATE_OPS)
    with tf.control_dependencies(update_ops), tf.name_scope('train'):
        train_op = optimizer.minimize(loss, global_step)

    metrics = {
        'global_step': tf.train.get_or_create_global_step(),
        'loss': loss,
        'cross_loss': cross_loss,
        'reg_loss': reg_loss,
        'learning_rate': learning_rate,
        'current_epoch': current_epoch,
    }

    # Logging drop_fraction if dynamic sparse training.
    if training_method in ('set', 'momentum', 'rigl', 'static'):
        metrics['drop_fraction'] = optimizer.drop_fraction

    # Let's log some statistics from a single parameter-mask couple.
    # This is useful for debugging.
    test_var = pruning.get_weights()[0]
    test_var_mask = pruning.get_masks()[0]
    metrics.update({
        'fw_nz_weight': tf.count_nonzero(test_var),
        'fw_nz_mask': tf.count_nonzero(test_var_mask),
        'fw_l1_weight': tf.reduce_sum(tf.abs(test_var))
    })

    masks = pruning.get_masks()
    global_sparsity = sparse_utils.calculate_sparsity(masks)
    metrics['global_sparsity'] = global_sparsity
    metrics.update(
        utils.mask_summaries(masks[:4] + masks[-1:],
                             with_img=FLAGS.log_mask_imgs_each_iteration))

    host_call = (functools.partial(utils.host_call_fn,
                                   output_dir), utils.format_tensors(metrics))

    return host_call, train_op
Ejemplo n.º 7
0
def train_fn(training_method, global_step, total_loss, train_dir, accuracy,
             top_5_accuracy):
  """Training script for resnet model.

  Args:
   training_method: specifies the method used to sparsify networks.
   global_step: the current step of training/eval.
   total_loss: tensor float32 of the cross entropy + regularization losses.
   train_dir: string specifying where directory where summaries are saved.
   accuracy: tensor float32 batch classification accuracy.
   top_5_accuracy: tensor float32 batch classification accuracy (top_5 classes).

  Returns:
    hooks: summary tensors to be computed at each training step.
    eval_metrics: set to None during training.
    train_op: the optimization term.
  """
  # Rougly drops at every 30k steps.
  boundaries = [30000, 60000, 90000]
  if FLAGS.training_steps_multiplier != 1.0:
    multiplier = FLAGS.training_steps_multiplier
    boundaries = [int(x * multiplier) for x in boundaries]
    tf.logging.info(
        'Learning Rate boundaries are updated with multiplier:%.2f', multiplier)

  learning_rate = tf.train.piecewise_constant(
      global_step,
      boundaries,
      values=[0.1 / (5.**i) for i in range(len(boundaries) + 1)],
      name='lr_schedule')

  optimizer = tf.train.MomentumOptimizer(
      learning_rate, momentum=FLAGS.momentum, use_nesterov=True)

  if training_method == 'set':
    # We override the train op to also update the mask.
    optimizer = sparse_optimizers.SparseSETOptimizer(
        optimizer, begin_step=FLAGS.maskupdate_begin_step,
        end_step=FLAGS.maskupdate_end_step, grow_init=FLAGS.grow_init,
        frequency=FLAGS.maskupdate_frequency, drop_fraction=FLAGS.drop_fraction,
        drop_fraction_anneal=FLAGS.drop_fraction_anneal)
  elif training_method == 'static':
    # We override the train op to also update the mask.
    optimizer = sparse_optimizers.SparseStaticOptimizer(
        optimizer, begin_step=FLAGS.maskupdate_begin_step,
        end_step=FLAGS.maskupdate_end_step, grow_init=FLAGS.grow_init,
        frequency=FLAGS.maskupdate_frequency, drop_fraction=FLAGS.drop_fraction,
        drop_fraction_anneal=FLAGS.drop_fraction_anneal)
  elif training_method == 'momentum':
    # We override the train op to also update the mask.
    optimizer = sparse_optimizers.SparseMomentumOptimizer(
        optimizer, begin_step=FLAGS.maskupdate_begin_step,
        end_step=FLAGS.maskupdate_end_step, momentum=FLAGS.s_momentum,
        frequency=FLAGS.maskupdate_frequency, drop_fraction=FLAGS.drop_fraction,
        grow_init=FLAGS.grow_init,
        drop_fraction_anneal=FLAGS.drop_fraction_anneal, use_tpu=False)
  elif training_method == 'rigl':
    # We override the train op to also update the mask.
    optimizer = sparse_optimizers.SparseRigLOptimizer(
        optimizer, begin_step=FLAGS.maskupdate_begin_step,
        end_step=FLAGS.maskupdate_end_step, grow_init=FLAGS.grow_init,
        frequency=FLAGS.maskupdate_frequency,
        drop_fraction=FLAGS.drop_fraction,
        drop_fraction_anneal=FLAGS.drop_fraction_anneal,
        initial_acc_scale=FLAGS.rigl_acc_scale, use_tpu=False)
  elif training_method == 'snip':
    optimizer = sparse_optimizers.SparseSnipOptimizer(
        optimizer, mask_init_method=FLAGS.mask_init_method,
        default_sparsity=FLAGS.end_sparsity, use_tpu=False)
  elif training_method in ('scratch', 'baseline', 'prune'):
    pass
  else:
    raise ValueError('Unsupported pruning method: %s' % FLAGS.training_method)
  # Create the training op
  update_ops = tf.get_collection(tf.GraphKeys.UPDATE_OPS)
  with tf.control_dependencies(update_ops):
    train_op = optimizer.minimize(total_loss, global_step)

  if training_method == 'prune':
    # construct the necessary hparams string from the FLAGS
    hparams_string = ('begin_pruning_step={0},'
                      'sparsity_function_begin_step={0},'
                      'end_pruning_step={1},'
                      'sparsity_function_end_step={1},'
                      'target_sparsity={2},'
                      'pruning_frequency={3},'
                      'threshold_decay=0,'
                      'use_tpu={4}'.format(
                          FLAGS.sparsity_begin_step,
                          FLAGS.sparsity_end_step,
                          FLAGS.end_sparsity,
                          FLAGS.pruning_frequency,
                          False,
                      ))
    # Parse pruning hyperparameters
    pruning_hparams = pruning.get_pruning_hparams().parse(hparams_string)

    # Create a pruning object using the pruning hyperparameters
    pruning_obj = pruning.Pruning(pruning_hparams, global_step=global_step)

    tf.logging.info('starting mask update op')

    # We override the train op to also update the mask.
    with tf.control_dependencies([train_op]):
      train_op = pruning_obj.conditional_mask_update_op()

  masks = pruning.get_masks()
  mask_metrics = utils.mask_summaries(masks)
  for name, tensor in mask_metrics.items():
    tf.summary.scalar(name, tensor)

  tf.summary.scalar('learning_rate', learning_rate)
  tf.summary.scalar('accuracy', accuracy)
  tf.summary.scalar('total_loss', total_loss)
  tf.summary.scalar('top_5_accuracy', top_5_accuracy)
  # Logging drop_fraction if dynamic sparse training.
  if training_method in ('set', 'momentum', 'rigl', 'static'):
    tf.summary.scalar('drop_fraction', optimizer.drop_fraction)

  summary_op = tf.summary.merge_all()
  summary_hook = tf.train.SummarySaverHook(
      save_secs=300, output_dir=train_dir, summary_op=summary_op)
  hooks = [summary_hook]
  eval_metrics = None

  return hooks, eval_metrics, train_op